Prepare to have your textbooks rewritten Earth science majors. Or at least that might happen if new research into Earth’s magnetic field holds true. Gregory Ryskin from Northwestern has developed a new theory of what produces the field. Current theories, called dynamo theories, say that the field is a result of convection currents and rotation in the outer core. Since the outer core is a layer of molten, electrically conductive iron this creates a magnetic field, though the actual details are a bit more complicated than that. And of course, the operative term describing the current view is “theories”. Geophysicists haven’t worked out the final details, and the article mentions that computer models tend to produce different results.
Ryskin takes a radically different approach. He was looking to explain the constant changes in magnetic field strength in different regions. Currently, these are blamed on turbulence in the core. Ryskin based his theory on something else that is constantly changing: ocean currents. Saltwater is electrically conductive, so it could work similar to the molten iron of the core. One piece of evidence in support of the new theory is that changes in the strength of ocean currents have been linked to changes in magnetic fields. The theory also has some interesting consequences. Changes in ocean currents might be linked to geomagnetic field reversals. The movement of tectonic plates and landmasses alters the routes currents follow, and therefore would affect the Earth’s magnetic field. Climate changes that affect ocean currents would also have an effect on the magnetic field.
Ryskin himself is an interesting researcher as you can see on his faculty page. He’s a chemical and biological engineering professor at Northwestern. But a good deal of his work is on physics, and now, geology (all the recent articles listed on his page went to a physics journal, with the exception of one geology paper). Score one for multidisciplinarity? I think so. The traditional geologists don’t seem terribly excited by the new research. I wonder if it’s some slight bias against an outsider coming in and trying to rework a central tenet of their field. More likely, though, this is just another case of slow acceptance of new theories in science. The dynamo theory does a lot, so there’s no need to drop it at the first sign of something else. More evidence is needed.
Also, I seem to have lots of questions about how we could get this evidence. I feel that it would be relatively easy to test Ryskin’s theory directly. Couldn’t we just get a lab to make a model of Earth and the oceans, rotate it, and measure the magnetic fields? Or just pore over several years of data on magnetic fields and ocean currents from NASA and analyze it for correlations? I still like the dynamo theory after having read lots of books on the planets, but Ryskin’s theory makes me wonder about the very watery nature of Earth. The oceans are electrically conductive and the currents move relative to Earth’s rotation. Perhaps they could affect the strength of magnetic field, even if they aren’t the cause?
